Electro Voice P3000 Protected Light On All The Time

[opacheco]

Hi,

I am trying to found the cause why my EV P3000 is in Protect Mode On (two red from panel led are on all the time) all the time; After to determinate the section with the failure i found the channel B power section was the section with the problem bacause the Protect Mode Red Leds On (both channels) turning off after I desconected the connector CN2A.

I tested all the Power Transistors units and 4 Drivers (MJE15022 and MJE15023 and its 4 Drivers black ones in the cornes of heat sink) and are ok, the drivers, I tested the power 0.47 Ohms double ceramic resistors and are ok too. Do someone have seen this problem before and who have an idea in order to found the failure cause?

Thanks a lot,
opacheco

 

[Khron]

Safe to assume you've already read through the service manual..?

https://elektrotanya.com/electro-voice_p3000_sm.pdf/download.html

 

[opacheco]

Safe to assume you've already read through the service manual..?

https://elektrotanya.com/electro-voice_p3000_sm.pdf/download.html

Yes of course!! but nothing about of this problem!
opacheco

 

[Khron]

I haven't browsed through the entire schematic, but is it impossible to figure out what sort of conditions would trigger the activation of the protection mode? Like a certain DC threshold on the output, etc...

 

[opacheco]

I haven't browsed through the entire schematic, but is it impossible to figure out what sort of conditions would trigger the activation of the protection mode? Like a certain DC threshold on the output, etc...

Ok I will consider that point! But I would like to know if someone have have this kind of trouble before?

opacheco

 

[Whoops]

It's strange that all the Power Transistors are OK and it still is in Protection Mode.

I would do a complete Re-Cap of all the Lytic caps next

 

[opacheco]

It's strange that all the Power Transistors are OK and it still is in Protection Mode.

I would do a complete Re-Cap of all the Lytic caps next

You know what??…I found the channel 2 was the problem because I disconnected the CN2B conector the one goes for the protected system of the amp and the protected condition and front led was to off.

I checked all the transistors and emitters and bases resistors for the channel 2, in the process, I had to desolder all these parts, a hard work by the!. I tested some others traits or too like the 4 drivers on the end of aluminum sink and another little transistors; all in good electronic condition!

After I did the resolder all the parts in its places and power up, the amp was ok in its two channels without protected condition; everything was ok. Cold solder maybe?

Thanks
opacheco

 

[Whoops]

Cold solder maybe?

Lately I have had my fixes that were just Cold Or Broken solders, broken PCB pads.

The worst one, and very dificult to find was a Diode that measured fine when I used the DMM probes, but then after many weeks I finally found that one of the legs of the Diode was not making contact with the inside of the diode, what a weird fail, never seen this one before. The Amplifier was 5 minutes from being completely trashed as we couldn't find the problem

 

[NoisyIndividual]

The service manual describes the bias procedure on these amps. There is a pin header with various pins including bias -ve and bias +ve, where you measure the actual bias voltages.
Next to one of these bias pin is a pin carrying Vcc. If you accidentally short this to the adjacent bias pin you WILL blow stuff up. And you don't want to do that, trust me.

I always cover the Vcc pin with rubber sleeving or heat shrink before measuring.

 

[NoisyIndividual]

Actually I think I might be confusing this amp with the Powermate range from the same company.

Regardless, if anyone ever sees a Vcc pin 2.5mm from a Bias pin, this should fill you with dread and the utmost in caution.

 

[mobyd]

Along the back (closest to the "firewall") edge of the poweramp PCBs you'll find lots of 1/8 watt resistors, 2R2 and others. the air and moisture (and fog juice) flows over these and causes leg-rot. A good place to go looking for trouble.

 

[NoisyIndividual]

The mains transformers in these have temperature sensors (thermistor) buried in the windings, I have come across more than one where this is failed or intermittent. This is connected to the Protection circuitry and will stop the amp working.
You can substitute a fixed resistor if this is the case, though obviously you will lose the safety feature this was designed for.
Compare the values left and right and see if there is any marked difference between the two, maybe at room temperature and again with warm transformers after its done some work.

 

[opacheco]

Lately I have had my fixes that were just Cold Or Broken solders, broken PCB pads.

The worst one, and very dificult to find was a Diode that measured fine when I used the DMM probes, but then after many weeks I finally found that one of the legs of the Diode was not making contact with the inside of the diode, what a weird fail, never seen this one before. The Amplifier was 5 minutes from being completely trashed as we couldn't find the problem

Interesting repair notes!!
Thanks a lot for your shared experience!
opacheco

 

[opacheco]

The service manual describes the bias procedure on these amps. There is a pin header with various pins including bias -ve and bias +ve, where you measure the actual bias voltages.
Next to one of these bias pin is a pin carrying Vcc. If you accidentally short this to the adjacent bias pin you WILL blow stuff up. And you don't want to do that, trust me.

I always cover the Vcc pin with rubber sleeving or heat shrink before measuring.

I measured the bias while the protected condition and the bias was 0 Vdc. This was a very rare problem!

Thanks for comment
opacheco

 

[opacheco]

Along the back (closest to the "firewall") edge of the poweramp PCBs you'll find lots of 1/8 watt resistors, 2R2 and others. the air and moisture (and fog juice) flows over these and causes leg-rot. A good place to go looking for trouble.

Interesting notes!!
Thanks
opacheco.

 

[opacheco]

The mains transformers in these have temperature sensors (thermistor) buried in the windings, I have come across more than one where this is failed or intermittent. This is connected to the Protection circuitry and will stop the amp working.
You can substitute a fixed resistor if this is the case, though obviously you will lose the safety feature this was designed for.
Compare the values left and right and see if there is any marked difference between the two, maybe at room temperature and again with warm transformers after its done some work.

In my case the thermistores were ok!

Thanks for your comments.
opacheco